Data split between multiple sites

ABSTRACT

Splitting data in a wireless communications network. Data may be split to use multiple base stations for transmission to user equipment in order to improve the bandwith if a UE is on a cell edge, or may be split by user equipment for transmission to multiple base stations in order to improve handover. Data splitting may be performed at the Packet Data Convergence Protocol layer, at the Radio Link Control layer, or at the Media Access Control layer on user equipment or on a base station. Data may instead be split in a network node, such as in a serving gateway, in order to reduce X2 interface load or delay carrier aggregation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/578,735, filed Feb. 27, 2013, which is the National Stage entry ofPCT Application No. PCT/US2011/024438, filed Feb. 11, 2011. PCTApplication No. PCT/US2011/024438 claims the benefit of U.S. ProvisionalPatent Application No. 61/303,769, filed Feb. 12, 2010, and U.S.Provisional Patent Application No. 61/304,377, filed Feb. 12, 2010. Thecontents of U.S. patent application Ser. No. 13/578,735, PCT ApplicationNo. PCT/US2011/024438, U.S. Provisional Patent Application No.61/303,769, and U.S. Provisional Patent Application No. 61/304,377 areincorporated herein by reference in their respective entireties.

BACKGROUND

In order to support higher data rate and spectrum efficiency, the ThirdGeneration Partnership Project (3GPP) Long Term Evolution (LTE) systemhas been introduced into 3GPP Release 8 (R8). (LTE Release 8 may bereferred to herein as LTE R8 or R8-LTE.) In LTE, transmissions on theuplink are performed using Single Carrier Frequency Division MultipleAccess (SC-FDMA). In particular, the SC-FDMA used in the LTE uplink isbased on Discrete Fourier Transform Spread Orthogonal Frequency DivisionMultiplexing (DFT-S-OFDM) technology. As used hereafter, the termsSC-FDMA and DFT-S-OFDM are used interchangeably.

In LTE, a wireless transmit/receive unit (WTRU), alternatively referredto as a user equipment (UE), transmits on the uplink using a limited,contiguous set of assigned sub-carriers in a Frequency Division MultipleAccess (FDMA) arrangement. For example, if the overall OrthogonalFrequency Division Multiplexing (OFDM) signal or system bandwidth in theuplink is composed of useful sub-carriers numbered 1 to 100, a firstgiven WTRU may be assigned to transmit on sub-carriers 1-12, a secondWTRU may be assigned to transmit on sub-carriers 13-24, and so on. Whilethe different WTRUs may each transmit into a subset of the availabletransmission bandwidth, an evolved Node-B (eNodeB) serving the WTRUs mayreceive the composite uplink signal across the entire transmissionbandwidth.

LTE Advanced (which includes LTE Release 10 (R10), also referred toherein as LTE-A, LTE R10, or R10-LTE, and which may include futurereleases such as Release 11) is an enhancement of the LTE standard thatprovides a fully-compliant 4G upgrade path for LTE and 3G networks. InLTE-A, carrier aggregation is supported, and, unlike in LTE, multiplecarriers may be assigned to the uplink, downlink, or both.

In both LTE and LTE-A, a UE, and therefore a user, may experienceservice degradation at a cell edge. Throughput, quality of service(QoS), and other factors may be affected by interference from othercells when a UE is operated at the edge of a cell. What is needed in theart are methods and systems that leverage the capabilities of LTE-A toaddress the problems with US operation at the edge of a cell.

SUMMARY

Methods and systems splitting data in a wireless communications networkare disclosed. Data may be split to use multiple base stations fortransmission to user equipment, or may be split by user equipment fortransmission to multiple base stations. In an embodiment. data splittingmay be performed at the Packet Data Convergence Protocol (PDCP) layer.In an embodiment, data may be split at the Radio Link Control (RLC)layer. In an embodiment, data may be split at the Media Access Control(MAC) layer. In each of these embodiments, data may be split on userequipment and/or on a base station. In an embodiment, data may insteadbe split at the user plane, such as in a serving gateway. These andadditional aspects of the current disclosure are set forth in moredetail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of disclosed embodiments is betterunderstood when read in conjunction with the appended drawings. For thepurposes of illustration, there is shown in the drawings exemplaryembodiments; however, the subject matter is not limited to the specificelements and instrumentalities disclosed. In the drawings:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented.

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A.

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A.

FIG. 2 illustrates a non-limiting exemplary network and componentcarrier configuration.

FIG. 3 illustrates another non-limiting exemplary network and componentcarrier configuration.

FIG. 4 illustrates a non-limiting exemplary downlink data flow andsystem configuration.

FIG. 5 illustrates a non-limiting exemplary uplink data flow and systemconfiguration.

FIG. 6 illustrates a non-limiting exemplary method of splitting data.

FIG. 7 illustrates a non-limiting exemplary uplink data flow and systemconfiguration.

FIG. 8 illustrates a non-limiting exemplary method of splitting data.

FIG. 9 illustrates a non-limiting exemplary downlink data flow andsystem configuration.

FIG. 10 illustrates a non-limiting exemplary downlink data flow andsystem configuration.

FIG. 11 illustrates a non-limiting exemplary uplink data flow and systemconfiguration.

FIG. 12 illustrates a non-limiting exemplary downlink data flow andsystem configuration.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c. 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the networks 112. By way of example, the base stations 114 a, 114b may be a base transceiver station (BTS), a Node-B, an eNodeB, a HomeNode B, a Home eNodeB, a site controller, an access point (AP), awireless router, and the like. While the base stations 114 a, 114 b areeach depicted as a single element, it will be appreciated that the basestations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 14 a may be part of the RAN 104, which may also includeother base stations and/or network elements (not shown), such as a basestation controller (BSC), a radio network controller (RNC), relay nodes,etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (1R), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b.102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), OSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNodeB, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a. 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is physically locatedremote from the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 106.

The RAN 104 may include eNodeBs 140 a, 140 b, 140 c, though it will beappreciated that the RAN 104 may include any number of eNodeBs whileremaining consistent with an embodiment. The eNodeBs 140 a, 140 b, 140 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNodeBs 140 a, 140 b, 140 c may implement MIMO technology. Thus, theeNodeB 140 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNodeBs 140 a, 140 b, 140 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1C, theeNodeBs 140 a. 140 b, 140 c may communicate with one another over an X2interface.

The core network 106 shown in FIG. 1C may include a mobility managementgateway (MME) 142, a serving gateway 144, and a packet data network(PDN) gateway 146. While each of the foregoing elements are depicted aspart of the core network 106, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 142 may be connected to each of the eNodeBs 142 a, 142 b, 142 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 142 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 142 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as OSM or WCDMA.

The serving gateway 144 may be connected to each of the eNodeBs 140 a,140 b, 140 c in the RAN 104 via the S1 interface. The serving gateway144 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 144 may also perform otherfunctions, such as anchoring user planes during inter-eNodeB handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 144 may also be connected to the PDN gateway 146,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 106 may facilitate communications with other networks.For example, the core network 106 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 106 may include, or may communicate with, an IP gateway (e.g.,an 1P multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 106 and the PSTN 108. In addition, the corenetwork 106 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

The LTE downlink (DL) transmission scheme may be based on an OFDMA airinterface. For the LTE uplink (UL) direction single-carrier (SC)transmission based on DFT-spread OFDMA (DFT-S-OFDMA) may be used. In theR8 LTE DL direction, a UE may be allocated by an eNodeB to receive itsdata anywhere across the whole LTE transmission bandwidth (e.g., anOFDMA scheme may be used.) The LTE DL may have an unused DC offsetsubcarrier in the center of the spectrum. In the R8 LTE UL direction,the R8 LTE system may be based on DTF-S-OFDMA or SC-FDMA transmission.

While a UE may, in the DL direction, receive its signal anywhere acrossthe frequency domain of the entire LTE transmission bandwidth, in the ULdirection a UE may transmit on a limited (or only on a limited), yet inan embodiment contiguous, set of assigned subcarriers in an FrequencyDivision Multiple Access (FDMA) arrangement. This arrangement may bereferred to as Single Carrier (SC) FDMA. In an embodiment, if theoverall OFDM signal or system bandwidth in the UL is composed of usefulsubcarriers numbered 1 to 100, a first given UE may be assigned totransmit its own signal on sub-carriers 1-12, a second given UE maytransmit on subcarriers 13-24, and so on. An eNodeB may receive thecomposite UL signal across the entire transmission bandwidth from one ormore UEs in the same time, but each UE may transmit (or only transmit)into a subset of the available transmission bandwidth. DFT-S-OFDM in theUL may therefore be viewed as a conventional form of OFDM transmissionwith the additional constraint that the time-frequency resource assignedto a UE must consist of a set of frequency-consecutive sub-carriers. Inthe UL, there may be no DC subcarrier. Frequency hopping may be appliedin one mode of operation to UL transmissions by a UE.

LTE-A may support carrier aggregation (CA) and flexible bandwidtharrangement features. This may allow DL and UL transmission bandwidthsto exceed 20 MHz (e.g., as in R8 LTE). For example, transmissionbandwidths of 40 MHz or up to 100 MHz may be supported. In LTE R10,component carriers (CC) may enable this spectrum aggregation feature. Inan embodiment, there may be up to 100 MHz aggregated spectrum, with 20MHz maximum bandwidth for each CC, and therefore at least 5 CCs. InLTE-A, different CCs may have different coverage.

In an embodiment utilizing multiple CCs, in order to prevent or mitigatemulticarrier interference, different cells may use different sets ofCCs. Such cells may have different ranges and may have effectivefrequency reuse patterns greater than 1, as illustrated in FIG. 2.

Carrier aggregation using multiple CC may be relevant for UEs in an RRCCONNECTED state. Idle UEs may access the network via a single UL and DLcarrier pair (e.g., using frequency division duplexing (FDD)). In anLTE-A embodiment, carrier aggregation in one serving eNodeB may besupported. This configuration may reduce the CA cell handover options tothe allocation of target candidate CCs after handover or beforehandover. Allocating target candidates after handover may increase userplane delay, therefore allocation before handover may provide betterperformance, and may require adding an X2 interface message formeasurement info exchange between a target and a source eNodeB.

It may be difficult to offer a uniform user experience (e.g.,throughput, QoS, etc.) when a UIE is at a cell edge because performanceat cell-edge may be limited by interference from other cells. In anembodiment, CCs may be used to mitigate the cell edge problem when a UEis in a good coverage area of a certain CC at a given time. In anembodiment, overlaying CCs may be created with different cell edges bycoordinating adjacent eNodeBs (cell sites) to vary the transmit power ofeach CC in a way that changes the distance to the cell edge, as show inFIG. 3.

In FIG. 3, UE 350 may be at position. 310 and may be communicating 371 avia CC 320 with eNodeB 361, and may be communicating 372 a via CC 330with eNodeB 361. As UE 350 moves to new position 311, where CC 330 maybe used with eNodeB 362, but CC 320 which, remains within the cellboundary of eNodeB 361, UE 350 may still communicate 371 b via CC 320with eNodeB 361, but may now communicate 372 b via CC 330 with eNodeB362. This may enable UE 350 to stay near a cell center by handing overto different CCs at different locations while the network maintains afrequency reuse factor of 1. In this scenario, full capability basestations (including those with and without an associated radio head(RRH)) may be used that are each capable of supporting UEs on all CCsand where UEs are capable of receiving on a set of CCs in which each CCmay be transmitted from a different site.

Note that while eNodeB 361 and eNodeB 362 are referred to as eNodeBs,these network elements may be any other type of device and/or networkelement that is capable of performing the functions described herein.For example, eNodeB 361 and/or eNodeB 362 may be a remote radio head(RRH), a sector antenna, any type of base station, or any combination ofthese or any other network element. Any such device or network elementmay be configured to perform any of the functions described herein thatare described as being performed by a base station, eNodeB, gateway,node, or any other network element, and all such embodiments arecontemplated as within the scope of the present disclosure.

In some LTE R10 implementations, support of multiple CCs for carrieraggregation may be limited to one serving eNodeB. This may prevent a UEfrom maintaining a data connection using one CC with different eNodeBs.In the scenario where a UE moves into a location where there is acoverage overlap for a CC on two different eNodeBs as shown in FIG. 3,the network radio resource management (RRM) entity may determine whetherto handover to another cell site instead of taking full advantage of thedata throughput increase by using multiple CCs from different sites. Inorder to take fill advantage of available bandwidth on each CC, thecorresponding data stream may be routed to and from the associatedeNodeB.

Each data stream has associated resources (bandwidth and buffer) used tosupport transmission and reception. The aggregate bandwidth for each CCmay be known by a network planner but the instantaneous bandwidthavailable for a UE on a CC is typically a dynamic decision of an eNodeBscheduler. The decision of how much data to send to each CC may have adirect impact on the resource requirements of each cooperating site. Inan embodiment, a cooperating eNodeB may feed back information on itsavailable resources, for example, to a serving eNodeB that may determineif and how to perform data splitting, and that may be configured toreceive the complete (e.g., split ratio or unsplit) data flow.

In an embodiment, the data throughput of a service architectureevolution (SAE) bearer from eNodeB to a UE may be increased bycoordinate splitting of data stream to multiple sites in the radioaccess network (RAN). The data splitting may be implemented at any layerof the RAN stack, including at the Packet Data Convergence Protocollayer (PDCP), the Radio Link Control (RLC) layer, the Media AccessControl (MAC) layer, or at any combination or using any means asdisclosed herein. Data splitting may also occur in the user plane.Systems and methods for performing such data splitting are disclosed inmore detail herein.

Uplink data and downlink data may be split across multiple eNodeBs andother sites (e.g., an RRH) in the RAN. For DL data splitting, an eNodeBmay split the incoming data stream into N streams corresponding to thenumber of cooperating CCs. Data splitting may be based on bandwidthavailability as reported by cooperating CCs, a buffer status as reportedfrom the buffering entity, and/or the data rate from bearer QoSrequirement. An eNodeB may also support interactive procedures todetermine how to split data, such as a loading sensitive mechanism. Thismechanism may use an algorithm that is based on the instantaneous bufferstatus, another measure of buffer status (e.g., average) and/orbandwidth of an existing entity on the peer eNodeB. The flow controlmechanism may be capable of buffering the data that is not yetacknowledged in order to recover from unrecoverable transmission errorson any of the cooperating CCs and/or buffering the data received fromthe data splitting entity and transmit it based on the bandwidthavailability.

In DL data splitting, an eNodeB may also support the ability to add orremove cooperating CCs dynamically without tearing down the SAE bearer.The eNodeB may also support load monitoring of the transmission path inorder to provide periodic and/or event triggered measurement reports onthe current buffer status to the data splitting entity and to provideperiodic and/or event triggered measurement report on the bandwidthutilization.

In DL data splitting, a UE may buffer the received data and performreordering of the data received from different links to make sure thatthe data is provided to the upper layers in the order it was sent. Thisfunctionality may be used where layers above the entity do generallydoes not have the ability to perform such reordering (e.g., such as nothaving the ability to perform such reordering in the normal course ofoperation). A UE may also support in-sequence delivery and may configureaffected layers to set up a data path that corresponds to the datastream splits.

In DL data splitting, the X2 interface (e.g., tunneling) may supportcertain functions. The X2 application protocol (X2 AP) may provide theconfiguration and controls of the data split entities and may beresponsible for delivering measurement and/or bandwidth monitoringreports and delivering entity setup, modification, and/or releaseconfiguration. The X2 data transport or tunneling protocol may connectthe data split entities between serving and cooperating eNodeBs toprovide transmit and/or receipt of data between connected eNodeBs and/ortransfer data control messages (e.g., reset messages, buffer status,bandwidth monitoring reports, etc.) between the two connected entities.The X2 data transport or tunneling protocol may also support flowcontrol exchange over either the X2 AP or via in-band signaling throughthe tunneling protocol.

In UL data splitting, a UE may split the incoming data stream into Nstreams corresponding to the number of cooperating CCs. Data splittingmay be based on the bandwidth availability as scheduled by cooperatingCCs, the buffer status as reported from the buffering entity, and/or thedata rate from bearer QoS requirement. A UE may support a loadingsensitive flow control mechanism that uses an algorithm that is based onthe instantaneous or other measure (e.g., average) buffer status and/oreNodeB scheduled UL bandwidth. The flow control mechanism may be capableof buffering the data that is not yet acknowledged to recover fromunrecoverable transmission errors on any of the cooperating CCs and/orbuffering the data received from the data splitting entity and transmitit based on the bandwidth availability.

In UL data splitting, a UE may also support the configuration to add orremove cooperating CCs dynamically without tearing down the SAE Bearer.A UE may support load monitoring of transmission path to provideperiodic and/or event triggered measurement reports on the currentbuffer status to the data splitting entity and/or periodic and/or eventtriggered measurement report on the bandwidth utilization.

In UL data splitting, an eNodeB may be configured to schedule (with orwithout cooperating eNodeB synchronization) bandwidth to a UE and bufferreceived data and perform reordering of data received from differentlinks to ensure that the data is provided to the upper layers in theorder it was sent. This reordering functionality may be use where layersabove the entity does generally not have the ability to performreordering (e.g., such as not having the ability to perform suchreordering in the normal course of operation). An eNodeB may alsosupport in-sequence delivery and configuration of affected layers to setup a data path corresponding to the data stream splits.

In UL data splitting, the X2 interface (e.g., tunneling) may supportcertain functions. The X2 application protocol may provide theconfiguration, may control the data split entities, and may beresponsible for delivering measurement and/or bandwidth reports and/ordelivering entity setup, modification, and/or release configuration. Thetunneling protocol may connect the data split entity between serving andcooperating eNodeBs to provide for transmitting data between connectedeNodeBs and/or transfer data control messages (e.g., reset messages,measurement reports, etc.) between the two connected entities.

In an embodiment, data splitting may be performed at the PDCP layer. Aninterworking function (PDCP IWF) may be used at a source eNodeB toforward compressed IP packets (PDCP PDU) to a PDCP IWF at cooperatingeNodeB before forwarding to the RLC layer for transmit buffering. ThePDCP IWF may provide support for multiple radio bearers per SAE bearer.

FIG. 4 illustrates an exemplary DL data flow and system configurationthat may be used in data splitting embodiment performing data splittingat the PDCP layer. UE 401 may be in a location that allows it tocommunicate with both eNodeB 410 and eNodeB 420. IP packet 405 may bereceived at eNodeB 410 and may have UE 401 as its destination. IP packet405 may be transmitted to eNodeB 410 vie SAE bearer 402, which mayinclude radio bearers 403 a and 403 b. PDCP IWF 450 may facilitatesplitting data between eNodeB 410 and eNodeB 420, in part with the useof inter-eNodeB tunnel 440.

IP header compression may be performed at header compression modules 411a and 411 b to reduce the number of bits needed to transmit over theradio interface. Robust header compression may be used, in any mode(e.g., unidirectional mode (U-mode), bidirectional optimistic mode(O-mode), and bidirectional reliable mode (R-mode)). O-mode and R-modemay utilize a feedback channel for error recovery. Because compressionuses prior frame information, header compression processing performed byheader compression modules 411 a and 411 b may be performed before datasplitting with feedback processing being performed in one entity (e.g.,only in one entity).

Ciphering and integrity protection of the transmitted data may beperformed at ciphering modules 412 a and 412 b. Inter-eNodeB tunnel 440may carry a portion of the PDCP PDU as a split data stream sub-flow tocooperating eNodeB 420 but after ciphering to avoid having to signal andmaintain multiple hyper-frame numbers (HFN) and PDCP sequence numbers(SN).

Data may be split at the PDCP Inter-eNodeB multiplexer 413, and the datasplit off for eNodeB 420 may be transmitted to eNodeB 420 viaInter-eNodeB Tunnel 440. The data that is to be transmitted from eNodeB410 may be provided to RLC buffers 414 a and 414 b, multiplexed at theMAC layer by MAC multiplexer 415, modulated and encoded at the physicallayer by PHY Modulation and Coding module 417, and ultimatelytransmitted to UE 401 via CC 471. The data that is to be transmittedfrom eNodeB 420 may be provided to RLC buffers 424 a and 424 b,multiplexed at the MAC layer by MAC multiplexer 425, modulated andencoded at the physical layer by PHY Modulation and Coding module 427,and ultimately transmitted to UE 401 via CC 472. eNodeB 410 and eNodeB420 may have MAC schedulers 416 and 426, respectively, that receivechannel status data 419 and 429 from UE 401 (e.g., downlink channelquality information) and data from RLC buffers and coordinates thetransmission of data with the MAC multiplexers and PHY Modulation andCoding modules.

There may be one PDCP entity per radio bearer configured for a mobileterminal. To support data splitting, a scheduler (e.g., a simpleround-robin distribution of received PDCP packet to active sites orbased on some splitting algorithm with buffer status or transmit ratefeedback from destination eNodeB 420) may be used to forward a PDCP PDU(e.g., containing a portion of IP packet 405) to another site (e.g.,eNodeB 420) for transmit via another CC. This configuration provides fortwo or more (in an embodiment, depending on number of co-transmit sites)data streams (e.g., PDCP/RLC/MAC) set up per radio bearer (e.g., one perparticipating CC and N for a UE where N is total number of participatingCCs). The scheduler residing on the PDCP/RLC interface may beresponsible for the scheduling of data forwarding to different sites,including a main serving site and a cooperative site for furtherprocessing in RLC layer.

In PDCP IWF 450, a flow mechanism may be used to avoid loss of data inthe event of congested or limited physical layer (PHY) bandwidth atcooperating CCs causing a buffer overflow. The flow mechanism may be afeedback-over-tunneling protocol providing data buffer status (e.g., RLCbuffer occupancy) and/or instantaneous or some other measure ofbandwidth information for a cooperating CC.

The corresponding UL data split at the PDCP layer as shown in FIG. 5utilizes the same module layout as in DL, but reverses the data pathdirection. Note that for any of the functions performed as described inFIG. 4, the inverse function may be performed by the same modules and/orentities in FIG. 5, or such inverse functions may be performed bydifferent modules or entities. For example, the MAC multiplexers ofeNodeBs 410 and 420 may also perform demultiplexing for UL signals. BothDL and UL may be configured with a PDCP entity per each participatingCC. In FIG. 5, data merger may be performed at eNodeB 410 by a mergerentity of PDCP inter-eNodeB multiplexer 413. In an embodiment, physicallayer HARQ ACK/NACK may be handled independently with the transmittingcells.

In FIG. 5, the data that is to be transmitted from UE 401 may beprovided by PDCP IWF data split (not shown) to RLC buffers 434 a and 434b configured on UE 401, multiplexed at the MAC layer by MAC multiplexer435, modulated and encoded at the physical layer by PHY Modulation andCoding module 437, split and ultimately transmitted to eNodeB 410 via CC473 and eNodeB 420 via CC 474. Here again, eNodeB 410 and eNodeB 420 mayhave MAC schedulers 416 and 426, respectively, that receive channelstatus data 419 and 429 from UE 401 (e.g., uplink channel qualityinformation).

On a receiver (UE 401 in FIG. 4, or either eNodeB in FIG. 5), datamerger may be performed to remerge the data split and in embodimentswhere the connection is configured for “RLC—in sequence delivery”, themerger entity may perform this task instead of the RLC entity since anindividual RLC entity may have received a partial PDCP data stream. Thedata merger may have access to a buffer that may be used to storeout-of-order delivery due to different transmission path delay over anair interface (Iu). In FIG. 4, data merger may be performed at UE 401 bymerger entity 407. Data splitting at the PDCP layer may have minorimpact to established system architectures, requiring changes that arelimited to PDCP. This configuration may also minimize configurationchanges, and allow for independent PDCP PDU delivery from separateroutes/sites (e.g., eNodeBs, RRH, NodeB, etc.).

In implementations that do not use data splitting (or that limit datasplitting), a seamless handover may be guaranteed by the RAN with dataduplication during preparation before or during the handover (HO). Adata mute (tunneling to forward the data stream) between the source andtarget eNodeB may be established before the UE is commanded for HO.After successful HO, the source eNodeB may forward the PDCP packettransmission status (PDCP SN) to a target eNodeB to synchronize transmitstatus so that no packets are lost.

In data splitting embodiments, the corresponding HO procedure may beperformed in several ways. Note that the HO command may be modified tohandle multiple CCs. In an embodiment where handover occurs betweenserving and/or cooperating CCs, a handover similar to a conventionalhandover may be performed. The CC cooperation configurations may need tobe updated to maintain the cooperation structure and, where a handoverdestination cannot support the needed service quality, the cooperationstructure may need to be reorganized. Seamless data transmission may beassured with PDCP SN synchronization. In an embodiment where handoveroccurs between cooperating CCs, a subset of a conventional handoverprocedure may be performed, where tunneling may be established betweenthe source cooperating eNodeB and the target cooperating eNodeB. Dataforwarding may be handled by either a new tunneling protocol or byreusing an existing GPRS tunneling protocol (in an embodiment, with somemodification) between eNodeBs. Additional modification may be performedon handover preparation information (e.g., X2 signaling) and handovercommands (e.g., RRC peer message over the air) to indicate that aserving CC has not changed.

The X2 interface may support inter-eNodeB RESOURCE (e.g., cell capacity)STATUS REQUEST and UPDATE. Cell capacity may be provided in terms of apercentage of UL/DL guaranteed bit rate (GBR)/non-GBR/total physicalresource block (PRB) usage as well as UL/DL S1 transport network layer(TNL) load (e.g., low/medium/high/over load) or via a new IE that mayindicate a number of PDCP PDUs that may be waiting in the RLCtransmission buffer. For the purpose of estimating the availablebandwidth on cooperating CCs, this may be sufficient for PDCP level datasplitting and to optimize the splitting scheduler algorithm efficiency.

For establishing inter-site cooperating data split between CCs, the X2interface may be handled in several ways. Initial establishment may betreated as a partial handover, in which case the handover preparationinformation message may be used. In an embodiment, it may not benecessary to create a new X2 signaling protocol for this purpose. In anembodiment, a new X2 signaling message for a source eNodeB to request atarget eNodeB to allocate resources (e.g., PDCP/RLC/MAC) may be createdthat supports cooperative transmission. Such a message may carrysufficient information to support some minimum data rate and QoS. Notethat the architecture and configuration shown in FIGS. 4 and 5 may beused with any embodiment disclosed herein, including those that performdata splitting other than at the PDCP layer.

In an embodiment, data splitting may be performed at the RLC layer. Insuch embodiments, an acknowledge mode (AM) mode bearer may beconfigured, but the disclosure set forth herein may be implemented withbearers of other modes. Data splitting may be achieved by splitting asingle stream of data received from higher layers into multiple streamsof data. Each stream of the split data may be referred to as a flowherein. Each flow may be analogous to an RLC entity as it is currentlydefined in 3GPP standards documents. Each flow may be input into adevice (e.g., an eNodeB) as service data units (SDUs) with sequencenumbers and may be output from the device as a stream of SDUs. Withinthe device, the SDUs may be broken down into protocol data units (PDUs)and may be reassembled on a peer node.

On a transmitting entity, additional functionality performed at the RLClayer may include a data splitter entity that is responsible forsplitting the data into one or more flows. Each flow on the transmittingside is functionally equivalent to a current version of the RLC. Thedata split entity may ensure that all the SDUs it receives from upperlayers are buffered even if some of the SDUs are sent on a CC to aneNodeB so that the data can be retransmitted if there is a transmissionfailure, for example over the radio line, or some other problem betweenone of the CCs and the UE.

On the a receiving entity the flow is similar to current RLCfunctionality with the exception that the flow entity may not handlereordering SDUs. This function maybe performed by a data merge entity. Adata merge entity may receive inputs from one or more flows and maybuffer and reorder the SDUs before sending them to higher layers.

FIG. 6 illustrates method 600 of performing UL data splitting at the RLClayer. At block 605, an RLC entity on a UE may receives an SDU fromPDCP. At block 610, a determination is made as to whether data splittingis configured. Without data split configured, at block 615 RLC mayupdate the MAC layer with the buffer information and await a datarequest from MAC. If data splitting is configured, at block 620, thedata may be provided to the data split entity residing on the UE. Thedata split entity may split the data into multiple flows at block 625(where each flow may act like an RLC AM entity by itself). The decisionon how the data is to be split may be based on multiple factorsincluding the bandwidth available on each CC based on input from MAC andthe current buffer status on each flow. Once the data has been splitinto flows for each CC, at block 630 buffer occupancy information may beupdated for MAC, and the MAC entity may determine the scheduling of thedata for transmission over the air. The MAC scheduler may be modified toaccommodate the concept of multiple flows.

At block 635, the MAC scheduler entity may select data from each flowand forward it to PHY for transmission to the destination eNodeB over anair interface (Iu). Upon receiving data on each flow at the eNodeBs, atblock 640 appropriate control messages are exchanged between the UE andthe eNodeB on the same flow for acknowledging the data or for requestinga retransmission. Note that once the PDUs are assembled into an SDU, allthe flows may be transmitted to the primary eNodeB that has theconnection to the Enhanced Packet Core Network (EPC) for the given UE.As the flows are acting independently, any RLC control information(retransmission request, reset, etc.) may be handled by the appropriateentity that is handling the given flow. Because the correct entity ishandling the control information, latency in handling retransmissionrequests may be reduced.

The RLC entity on the primary eNodeB that receives the flows from otherRLC entities provides the data to a merge functionality or entity. Themerge entity is responsible for merging the received data and for makingsure that the data is in order before it is provided to PDCP.

FIG. 7 illustrates an exemplary data flow and architecture that may beused in accordance with an embodiment where RLC layer data splitting isperformed. UE 730 may receive data at PDCP layer 739 and provide thedata to RLC layer 737. At RLC layer 737, data split entity 736 splitsthe data into flows 731 and 732, which are provided to MAC 735. Datasplit entity 736 may track RLC SDUs as it divides the data into separateflows. MAC 735 may provide the data to PHY 734, which may transmitdistinct portions of the data over different CCs (as flows 731 and 732)to eNodeB 710 and eNodeB 720.

eNodeB 720 may receive the data at PHY 724 and provide it to MAC 725,which in turn provides the data of flow 732 to RLC 727. RLC 727 may thenprovide the flow data to eNodeB 710 via tunnel 740. At eNodeB 710, dataflow 731 may be received at PHY 714 which may provide it to MAC 715,which in turn provides the data of flow 731 to RLC 717. Data mergeentity 718 of RLC 717 may then merge the data flows into properlyordered SDUs and provide the resultant data to PDCP 719, which maytransmit the data as IP packets to a network. Data merge entity 718 maytrack RLC SDUs. X2 signaling 750 may be used to exchange controlinformation between eNodeB 710 and eNodeB 720.

FIG. 8 illustrates method 800 of performing DL data splitting at the RLClayer. At block 805, an RLC entity on an eNodeB entity that has contextwith the EPC for the given UE receives the data that is destined for theUE. In normal mode when there is no CC involved, this may result in achange in the total buffer occupancy for the channel. At block 810, theRLC entity on the eNodeB may determine whether data split is configured.If so, at block 820 the RLC entity may check with the data splittingentity to determine if the SDU is to be transmitted to the peer eNodeBor if it is available for local transmission. If data splitting is notconfigured, processing the received data may proceed normally at block815.

At block 820, the data splitting entity may determine if the data is tobe sent to the peer RLC or not based on a range of factors that mayinclude the bandwidth available at the peer entity, current bufferstatus of the peer entity, etc. As the instantaneous buffer status maynot be available over the X2 interface, the algorithm that determinesthe data split may determine the split based on assumed data rate or thelast reported measurements and predictions based on the time since thelast reported measurements.

If the data is to be sent on the local flow (i.e., from the eNodeBdirectly to the destination UE), buffer occupancy information may beprovided to MAC to be updated at block 825, and at block 830, the RLCmay transmit the data to the MAC layer when the data is requested. Thedata may be transmitted to the UE at block 835.

If the data is to be sent to a different eNodeB, it may be sent over theeNodeB-eNodeB tunnel to the peer eNodeB at block 840. The receiving RLCon the peer eNodeB may behave the same way as if it received the datafrom upper layers. The difference may be that the RLC transmissionstatus feedback (e.g., RLC buffer status and the information about SDUsnot transmitted) is forwarded to the RLC data split entity on the sourceeNodeB by the cooperating RLC entity. This may enable the data splitentity to transmit a failed packet over another available CC as well asmaintaining an up-to-date buffer status for a seamless handover.

The RLC entity on each CC may update the buffer occupancy information itprovides to the MAC layer. A MAC entity may schedule the datatransmission based on the data and bandwidth availabilities. On the UEside, upon receipt of data from the MAC the reassembly functionality maybe performed as per the current RLC standard independently for eachflow. If there is any RLC Control information that has to betransmitted, the MAC on the UE side may be informed of the flow on whichthe data is to be transmitted. Once the SDUs are formed they areprovided to the data merge functionality that is responsible forreordering the SDUs (if it is so configured). The SDUs may be orderedbefore they are sent out of RLC to the PDCP layer. Reordering may bedone based on the sequence numbers added to the SDU or based on thesequence number provided by PDCP.

FIG. 9 illustrates an exemplary data flow and architecture that may beused in accordance with an embodiment where RLC layer data splitting isperformed. eNodeB 910 may receive IP packets 990 at PDCP layer 919 andprovide the data to RLC layer 917. At RLC layer 917, data split entity918 may split the data into flows 931 and 932. Data split entity 918 maydetermine that flow 932 is to be transmitted to a peer eNodeB while flow931 is to be transmitted locally (i.e., directly to UE 930). Data splitentity 918 may provide flow 931 to MAC 915 (e.g., upon request afterupdating buffer occupancy information). Data split entity 918 may trackRLC SDUs as it divides the data into separate flows. MAC 915 may providethe data for flow 931 to PHY 914, which may transmit flow 931 over afirst CC to UE 930.

eNodeB Flow 910 may provide flow 932 to eNodeB 920 via tunnel 940. RLClayer 927 may provide flow 932 to MAC 925 (e.g., upon request afterupdating buffer occupancy information). MAC 925 may provide the data forflow 932 to PHY 924, which may transmit flow 932 over a second CC to UE930. X2 signaling 950 may be used to exchange control informationbetween eNodeB 910 and eNodeB 920.

At UE 930, data flows 931 and 932 may be received at PHY 934 which mayprovide them to MAC 935, which in turn provides the data of flows 931and 932 to RLC 937. Data merge entity 936 of RLC 937 may then merge thedata flows into properly ordered SDUs and provide the resultant data toPDCP 939, which may transmit the data as IP packets to a network. Datamerge entity 938 may track RLC SDUs.

For RLC layer data splitting embodiment, handover operations may beperformed using any means or methods disclosed herein, including themean disclosed in regards to PDCP layer data splitting.

In an embodiment, data splitting may be performed at the MAC layer. AMAC IWF may be configured on a source eNodeB that forwards RLC packets(e.g., PDUs) to a MAC IWF configured on a cooperating eNodeB that mayprovide transmit buffering. Note that MAC layer data splitting may beapplied as described herein to high speed packet access (HSPA)configurations as well as LTE and LTE-A configurations. In an HSPAconfiguration, a serving eNodeB in LTE-A may be equivalent to a servingradio network controller (RNC) in HSPA, and a cooperating eNodeB inLTE-A may be equivalent to a NodeB or an RNC in HSPA.

FIG. 10 illustrates an exemplary DL data flow and architecture that maybe used in accordance with an embodiment where MAC layer data splittingis performed. eNodeB 1010 may receive IP packets 1090 at PDCPs 1019 aand 1019 b which may perform PDCP encoding and provide the data to RLCbuffers layer 1017 a and 1017 b. RLC buffers 1017 a and 1017 b mayprovide the data to MAC 1015, which may include multiplexing entity 1019that may determine the appropriate data split and splits the data intoat least two portions. Multiplexing entity 1019 may take into accountthe available bandwidth for peer eNodeBs, and may forward the RLC PDU inperforming data multiplexing. The data that is determined to be sentusing a peer eNodeB may be provided to eNodeB 1020 by forwarding entity1018 via inter-eNodeB tunnel 1040. The data that is determined to betransmitted locally (i.e., directly from eNodeB 1010 to UE 1030 may beprovided to hybrid ARQ (HARQ) entity 1016 that may perform any HARQfunctions, and forward the data to PHY 1014 for transmission 1061 usinga first CC to UE 1030.

eNodeB 1020, upon receipt of data for UE 1030 from eNodeB 1010 viainter-eNodeB tunnel 1040, may buffer such data at inter-eNodeB buffer1028. Buffer 1028 may provide the data to MAC 1025 for multiplexing bymultiplexing entity 1029 and HARQ functions performed by HARQ entity1026. The data may be provided to PHY 1024 for transmission 1062 using asecond CC to UE 1030.

MAC scheduler 1012 on serving eNodeB 1010 may use reported (e.g.,estimated or predetermined guaranteed or averaged transmission, etc.)supporting data rate from cooperating eNodeB 1020 as the reference inthe payload selection algorithm to request the RLC PDU to be forwardedto cooperating inter-site CC for transmission.

MAC scheduler 1022 at cooperating eNodeB 1020 may report (e.g., anestimated, predetermined, or calculated guaranteed or averagetransmission, etc.) data rate that can be supported on eNodeB 1020 toserving eNodeB 1010 on a periodic basis, updating the supporting ratewhile a connection exists between the two eNodeB. This and other controlinformation may be exchanged between eNodeBs via X2 signaling interface1050. In an embodiment, X2 interface per cell radio resource status maybe requested but the update of radio resource status that provides DL/ULGBR/non-GBR/Total PRB may be optional. The PRB status may also be usedas an alternative for scheduling input if such information is available.

MAC scheduler 1022 at cooperating eNodeB 1020 may also perform standardpayload selection for the cooperating CC using the RLC PDU buffersavailable in inter-eNodeB buffer 1028 either as a fixed size PDU orresize by multiplexing 1029 for available radio resources. RLC PDU sizeselection may be performed by serving eNodeB MAC scheduler 1012 toaccommodate the reported supporting data rate or the guaranteed rate.

MAC inter-eNodeB data forwarding entity 1018 on eNodeB 1010 may be apassive relay unit that may deliver MAC data to PHY for processingand/or to eNodeB 1020 via tunnel 1040.

MAC inter-eNodeB buffer 1028 at cooperating eNodeB 1020 may serve as atemporary “parking” area on cooperating eNodeB 1020 to accommodatevariable latency that may be due to data tunneling on X2 interface.

Inter-site tunnel 1040 may be a data pipe that forwards RLC PDUs fromserving eNodeB 1010 to cooperating eNodeB 1020. There may be one tunnelper each cooperating eNodeB.

The configuration and data flow described herein in regard to FIG. 10and MAC layer data splitting may be implemented with minor impact to thesystem architecture and with changes limited to the MAC layer. Suchchanges may be minimal, and may be configuration changes that may be thesame or with minor differences from those required to supportCoordinated Multipoint Transmission (CoMP) procedures. In an embodiment,some of the CoMP procedures may be reused with some modification. In anembodiment, air interface resource reservation for participating sitesmay be used to reduce X2 interface delay. RLC SDU or in-sequencedelivery may require that all relevant RLC PDUs be received correctlybefore RLC can deliver them to the upper layers. Note that the RLC PDUsmay be transmitted over two different physical layer interfaces, each ofwhich may have different latency than the other. Therefore, there may bea requirement on a receiving RLC entity to buffer additional input data.The cooperating CC may need to transmit the RLC PDU within the upperlayer retransmit timer limit.

The corresponding UL MAC layer data split data flows and architecturesare illustrated in FIG. 11, using the same devices and entitiesdescribed for FIG. 10. The functions shown in FIG. 11 may be mostly orentirely compatible with existing LTE and/or LTE-A signaling structures,but may also include the enhancement of the configuration for multipleCCs and corresponding scheduling from network. The corresponding networkrequirement to forward successfully received MAC PDUs to RLC on aserving eNodeB may be the same as what is needed to introduce CoMPprocedures.

In FIG. 11, data may be received at RLC buffers 1037 a and 1037 b on UE1030, and may be provided to MAC multiplexing entity 1039 that maydetermine the data split and provide the data to PHY 1034 fortransmission on separate CCs 1063 and 1064 to eNodeB 1010 and 1020,respectively. Priority handling data may be used by MAC multiplexingentity 1039. Such data may be exchanged between priority handling entity1032 and MAC schedulers 1012 and 1022. Upon receipt of data directlyfrom UE 1030, PHY 1014 of eNodeB 1010 may provide the data to MAC 1015,which may perform HARQ functions and provide the data to multiplexingentity 1019. Multiplexing entity 1019 may demultiplex the data with thedata received from eNodeB 1020 via tunnel 1040. Upon receipt of datadirectly from UE 1030, PHY 1024 of eNodeB 1020 may provide the data toMAC 1025, which may perform HARQ functions and provide the data tomultiplexing entity 1029, which may demultiplex the data and provide itto eNodeB 1010 via tunnel 1040. After demultiplexing, the data may beprovided to RLC buffers 1017 a and 1017 b, PDCP decoders 1019 a and 1019b, and then transmitted to the network as IP packets 1091. Buffer status1073 and 1074 may be provided by UE 1030 to MAC schedulers 1012 and1022, respectively.

In MAC layer data splitting embodiments, basic handover featuressupported by LTE R8 may support handover as described herein with theaddition of a configuration that supports reorganizing and/ormaintaining a cooperation structure and support of partial handover onthe X2 signaling interface. Partial handover of a serving CC orcooperating CCs may use the establishment of an additional data pathbetween eNodeBs. There may be no need for data copy since MAC packetlost during path establishment or reestablishment may be handledautonomously with RLC level retransmission (for cooperating CC handoversince RLC is always on the serving CC and may not have moved) or PDCPretransmission (for serving CC handover since PDCP transmission statusis forwarded to a target cell). The X2 handover signal interface mayencapsulate the handover preparation information defined by the RRClayer. Therefore, the signaling issue of communicating a partialhandover may be addressed with the modification of an RRC handovermessage to provide the context of the cooperation structure in handoverpreparation information.

In an embodiment, user plane data splitting may be implemented in anexemplary system. In PDCP layer, RLC layer, MAC layer, or servinggateway data splitting, or in a system that uses any combination of anyof these and/or any other means disclosed herein, for an efficientdata-splitting decision, the serving eNodeB may need to take intoaccount the resources available and local scheduling information fromthe remote eNodeBs. In RAN data splitting embodiments, a specialized“inter-working function” may be used to buffer downlink frames tomitigate the delay introduced by X2 link. The serving eNodeB mayconsider the X2 delay and may reduce X2 latency by initiating a servinggateway (S-GW) data-split instead of a RAN data split. Upon determiningthat data splitting is to be used, a serving eNodeB may transmit acontrol signal to a serving gateway instructing the serving gateway tobegin splitting data.

In an embodiment, user-plane load on the X2 interface may be reduced bybuilding the framework to allow the data-splitting to occur at theServing Gateway, and extending the LTE R8 handover to allow forcarrier-specific handover. In order to implement such an embodiment, amessage sequence that allows a serving eNodeB to indicate thecarrier-specific handover decision to the Serving Gateway and enable itto split the UE traffic in a carrier-specific manner may be used. In anembodiment implementing carrier-specific handover, eNodeB-MME messagingmay be extended to support an indication of a handover of a list ofaffected radio access bearers (RABs), and require the MME to supportcarrier-specific PATH_SWITCH_REQUEST messages.

In an embodiment, for example as shown in FIG. 3 where UE 350 may beconnected to two eNodeBs when at position 311, proper RRC signaling maybe needed to support a split RRC connection. In some implementations, aneNodeB LYE context may be established when the transition to an activestate for a UE is completed or in a target eNodeB after completion of ahandover resource allocation during handover preparation. An eNodeB UEcontext may be a block of information in an eNodeB associated with oneactive UE. This block of information may contain the necessaryinformation required to maintain the E-UTRAN services towards the activeUE. UE state information, security information, UE capabilityinformation and the identities of the UE-associated logicalS1-connection may be included in the eNodeB UE context.

In an embodiment, user plane data splitting may be performed at aserving gateway, as illustrated in FIG. 12. IP packets 405 may bereceived at packet data network (PDN) gateway 1210 and transmitted toserving gateway 1220. Serving gateway 1220 may split the data andtransmit one portion of the data to eNodeB 1230 via S bearer 1251 andthe other portion of the data to eNodeB 1240 via S1 bearer 1252. eNodeBs1230 and 1240 may then transmit the data to UE 1270 via radio bearers.Unacknowledged PDCP SDUs 1261 and 1262 may be transferred betweeneNodeBs to allow for lossless handover. Data-splitting for bearersassociated with individual CCs at the serving gateway may be enabledbased on input from the eNodeB and/or a load-balancing algorithm runningon the Serving Gateway. A single component carrier may be associatedwith a HARQ entity. Logical channels may be transparently mapped to thedifferent component carriers.

When a CC is handed over from one eNodeB (source) to another (target),the source eNodeB may indicate to the MME associated with the ServingGateway (either directly or through a target eNodeB) the radio bearersthat were being carried on the component carrier. This may be achievedby creating a message to be transmitted from the source eNodeB to theMME associated with the Serving Gateway, or by extending the Path SwitchRequest Message.

The Path Switch Message may be exchanged between an eNodeB and an MME torequest the switch of a downlink GPRS tunneling protocol (GTP) tunneltowards a new GTP tunnel endpoint. The Path Switch Message may carry theEUTRAN RAB (E-RAB) to be switched in the Downlink List informationelement (IE), which may be the list of all the E-RABs that need to beswitched from the source eNodeB to target eNodeBs. If the E-RAB to beswitched in the Downlink List IE in the PATH SWITCH REQUEST message maynot include all E-RABs previously included in the UE Context, the MMEmay consider the non included E-RABs as implicitly released by theeNodeB.

To support carrier-specific handover, the Path Switch Request (or analternate message) may carry a list of RABs that need to be switched.However, the MME and Serving Gateway may continue forwarding the rest ofthe traffic to the source eNodeB as before.

An eNodeB may determine how to request the splitting of data at theServing Gateway (S-GW). In an embodiment, an eNodeB may requestdata-splitting at the RAB level, in which case the Path Switch Messagemay include a list of all RABs that need to be split. If the eNodeB doesnot want to split data at the RAB level, it may send an indicator withthe percentage of traffic that should be redirected to the new eNodeB.In an embodiment, a “RAB to keep” list may be used to avoid potentialcompatibility or interpretation issues with older equipment. A servingeNodeB may also implement a muting algorithm to decide the optimumRAB/RB mapping based on AS information that may not be available to MME.An optional IE that provide routing suggestions may be included in the“PATH SWITCH REQUEST” where MME/S-GW may decide to adopt the data splitrouting as suggested by an eNodeB or alternatives. Some potential activeinputs to the decision of determining data split routing may includeRB/RAB split assignment (mapping of RAB/RB to specific eNodeB MACaddress), percentage of data split, and other inputs.

Partial data from a radio bearer may be sent on a component carrier, andthis may be indicated by a special indicator to allow the ServingGateway the option to split the traffic to mirror a similar arrangement.The special indicator may be a one-time event, or a periodicnotification from the serving eNodeB to the S-GW/MME to change thesplitting ratio based on channel quality measurements.

MME/S-GW may implement some routing intelligence that is used to makethe data flow split decision based on eNodeB-provided status inputs.Such inputs may include available eNodeB (e.g., PDCP) buffer, meantransmission latency (e.g., on UE or per specific RAB/RB), supportabletraffic loading distribution (e.g., % load per eNodeB), and others.

Note that the packets sent from an S-GW may be IP traffic encapsulatedin GTP tunnels, and may require the creation of two GTP tunnels, oneterminating at the source eNodeB and another terminating at the targeteNodeB for a single E-RAB identity. This may vary from someimplementations that mandate a one-to-one RAB to radio bearer mapping.

In an embodiment, a UE may have one RRC connection with the network,with one special cell that would provide security and NAS information.Referring again to FIG. 3, at startup, UE 350 at position 311 isassociated with an RRC connection with eNodeB 361, and establishedcomponent carrier set of CC 320 and CC 330B. Hence, UE 350 may beassociated with a serving cell (or special cell) at eNodeB 361, and mayget the security and NAS mobility information from eNodeB 361 until aserving cell handover takes place.

To support mobility in the co-operative component carrier deployment,where CC 330 is a serving cell, UE 350 moving to position 311 may causean RRC Connection Handover, signaled using RRC ConnectionReconfiguration, and may cause the reset of the MAC/RLC layers toaccount for new security parameters. In an embodiment where CC 330 isnot a serving cell, UE 350 may maintain its RRC Connection with eNodeB361 as it moves from position 310 to Position 311. Security proceduresmay need additional mechanisms for handover as described below.

An eNodeB UE context may be established when the transition to activestate for a UE is completed or in a target eNodeB after completion ofhandover resource allocation during handover preparation. In anembodiment, a handover procedure may trigger the target eNodeB and theUE to generate fresh keys for a ciphering and encryption algorithm,derived from a {K_(eNB*), NCC} pair sent from a source eNodeB. Thetarget eNodeB may use this tuple to generate a fresh K_(eNB). TheK_(UPene) key (derived from K_(eNB)) may be used for the protection ofuser plane traffic with a particular encryption algorithm.

In an embodiment where UE 350 of FIG. 3 maintains an RRC Connection withsource eNodeB 361 as it moves from, for example, from position 310 toposition 311, the PDCP entity running in target eNodeB 362 may need tocontinue using the same keys as source eNodeB 361. This may allow the UEto receive PDCP entities from different eNodeBs simultaneously. Thesekeys may be exchanged with the Handover Command in the handoverpreparation phase of handover from the source eNodeB to the targeteNodeB. In an embodiment, this information may be conveyed during theinitial Context Setup from the S-GW.

In an embodiment, uplink reports, including power headroom, bufferstatus reports, and channel quality reports, may be available at atarget eNodeB, and may either be transferred from a source eNodeB totarget eNB over X2-AP, or the UE may send the reports separately to thetwo eNodeBs. To provide backward compatibility, the UE may send thereports on the serving cell to the “serving eNodeB”. However, this mayintroduces latency in the availability of input for the scheduler at thetarget eNodeB, which may result in some implementations in non-optimumscheduling decisions.

In order to properly support handover in LTE-A with carrier aggregation,per carrier UE measurement and reporting over aggregated downlinkcarriers may need to be defined, including carrier-specific RSRP and/orRSRQ. LTE R8 mechanisms may not support intra-frequency measurementsbecause measurements may be based on serving cells. For example, aneNodeB may own three carriers F1, F2, and F3, and may be using F1 andF2, and F1 may be the serving cell. When the signal quality of F3 isbetter than F2, it may be desirable to have a measurement scheme tohandle this situation so that the UE can report this situation.Carrier-specific measurements, including from non-serving cells, may bedesired in some implementations.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

The invention claimed is:
 1. A wireless transmit and receive unit (WTRU)comprising: a processor; and a memory comprising instructions that whenexecuted by the processor cause the WTRU to: establish a first radiobearer, wherein data that is transmitted to the WTRU via the first radiobearer is divided by a Packet Data Convergence Protocol (PDCP) entity ofa first evolved Node-B (eNB) into a first portion and a second portion,the first portion being delivered to the WTRU via the first eNB and thesecond portion being delivered to the WTRU via a second eNB; receive,via a first cell that is associated with the first eNB, at least a firstPDCP packet data unit (PDU) associated with the first portion of thedata that is transmitted to the WTRU via the first radio bearer;receive, via a second cell that is associated with the second eNB, atleast a second PDCP PDU associated with the second portion of the datathat is transmitted to the WTRU via the first radio bearer; and reorderat least the first and second PDCP PDUs at a PDCP layer of the WTRU. 2.The WTRU of claim 1, wherein the instructions, when executed by theprocessor, further cause the WTRU to buffer at least one of the firstPDCP PDU or the second PDCP PDU.
 3. The WTRU of claim 1, wherein thesecond portion is transmitted by the first eNB to the second eNB via anX2 interface.
 4. The WTRU of claim 1, wherein the data that istransmitted to the WTRU via the first radio bearer comprises InternetProtocol (IP) packets.
 5. A method comprising: by a wireless transmitand receive unit (WTRU), establishing a first radio bearer, wherein datathat is transmitted to the WTRU via the first radio bearer is divided bya Packet Data Convergence Protocol (PDCP) entity of a first evolvedNode-B (eNB) into a first portion and a second portion, the firstportion being delivered to the WTRU via the first eNB and the secondportion being delivered to the WTRU via a second eNB; receiving, via afirst cell that is associated with the first eNB, at least a first PDCPpacket data unit (PDU) associated with the first portion of the datathat is transmitted to the WTRU via the first radio bearer; receiving,via a second cell that is associated with the second eNB, at least asecond PDCP PDU associated with the second portion of the data that istransmitted to the WTRU via the first radio bearer; and reordering atleast the first and second PDCP PDUs at a PDCP layer of the WTRU.
 6. Themethod of claim 5, further comprising buffering at least one of thefirst PDCP PDU or the second PDCP PDU.
 7. The method of claim 5, whereinthe second portion is transmitted by the first eNB to the second eNB viaan X2 interface.
 8. The method of claim 5, wherein the data that istransmitted to the WTRU via the first radio bearer comprises InternetProtocol (IP) packets.